Enable pydocstyle (via flake8).

Author: Julian

.flake8

@@ -1,10 +1,16 @@
 [flake8]
 ban-relative-imports = true
 inline-quotes = "
+per-file-ignores =
+    noxfile.py:D
+    referencing/tests/*:D
+    referencing/_attrs.py:D
 ignore =
     # Barring function calls in default args. Ha, no.
     B008,
     # See https://github.com/PyCQA/flake8-bugbear/issues/131
     B306,
+    # This rule makes diffs uglier when expanding docstrings (and it's uglier)
+    D200,
     # (flake8 default) old PEP8 boolean operator line breaks
     W503,

noxfile.py

@@ -48,6 +48,7 @@ def style(session):
         "flake8-broken-line",
         "flake8-bugbear",
         "flake8-commas",
+        "flake8-docstrings",
         "flake8-quotes",
         "flake8-tidy-imports",
     )

referencing/__init__.py

@@ -1 +1,6 @@
-from referencing._core import Registry, Resource, Specification  # noqa: F401
+"""
+Cross-specification, implementation-agnostic JSON referencing.
+"""
+from referencing._core import Registry, Resource, Specification
+
+__all__ = ["Registry", "Resource", "Specification"]

referencing/_core.py

@@ -46,9 +46,15 @@ class Resource(Generic[D]):
 
     @classmethod
     def from_contents(cls, contents: D) -> Resource[D]:
+        """
+        Attempt to discern which specification applies to the given contents.
+        """
         return cls(contents=contents, specification=Specification.OPAQUE)
 
     def id(self) -> str | None:
+        """
+        Retrieve this resource's (specification-specific) identifier.
+        """
         return self._specification.id_of(self.contents)
 
 
@@ -82,7 +88,6 @@ def crawl(self) -> Registry[D]:
         """
         Immediately crawl all added resources, discovering subresources.
         """
-
         return self
 
     def with_resources(

referencing/typing.py

@@ -1,3 +1,6 @@
+"""
+Type-annotation related support for the referencing library.
+"""
 from __future__ import annotations
 
 from typing import TypeVar